1. Field of the Invention
The present invention relates to a method and apparatus for pumping or delivering fluids utilizing a flexible vessel that may be subject to controlled pressures and preferably located within a pressure vessel.
2. Description of the Prior Art
Current methods for pumping or delivering fluids, particularly biological fluids, include utilizing peristaltic (tubing) pumps, diaphragm pumps, and centrifugal pumps. Biological fluids encompass fluids that comprise, exist in or are used in or delivered to living organisms. Indeed, biological fluids may comprise pharmaceutical preparations (e.g., insulin, erythopoietin, or morphine) or biological preparations (e.g., liposomes, plasmids, naked DNA or transformed cells), bodily fluids and their components, such as blood cells, and other fluids that comprise biological components, including living organisms such as bacteria, cells or other cellular components. Biological fluids also may comprise whole blood or specific whole blood components, including red blood cells, platelets, buffy coat, white blood cells, precursor cells, progenitor cells; prokaryotic and eukaryotic cell suspensions, including recombinant, transformed, and transfected cells; viruses and viral preparations including recombinant viruses; membrane vesicle preparations, including lysosomes, endosomes, caveolae, micelles, and liposomes; molecule interactions including DNA-protein, RNA-protein, and protein-protein interactions; DNA preparations; RNA preparations; and protein preparations.
Certain fluid types, such as fluids comprising pressure or flow sensitive fluids, such as biological fluids, can be negatively affected by subjecting such fluids to such current pumping or delivering methods. For example, biological fluids comprising blood or its cellular components, may be damaged (e.g., cells may be lysed or membranes damaged) when exposed to perturbations and/or turbulence caused by such current methodologies. Moreover, these fluid types may also be negatively affected by inaccurate or inconsistent flow rates and pressures created by such current methods. In addition, drug delivery systems are negatively affected by such inaccurate or inconsistent flow rates.
One of the specific drawbacks, for example, with peristaltic pumps is that they are essentially positive displacement and have the potential to develop excessive pressures if an occlusion occurs within the pump or its components. When pumping or delivering biological fluids, such as whole blood or buffy coat, any excess pressure resulting from even a partial occlusion may result in cell membrane damage or hemolysis. Diaphragm pumps present difficulties in the measurement of fluid volume pumped when partial strokes are involved and may require auxiliary valving. Centrifugal pumps are difficult to track for volume pumped, cannot hold against a static head without check valves, are non-reversible, and generally require some mechanical rotor support in the fluid stream (e.g., a hydrodynamic bearing or magnetic system). The diaphragm and centrifugal pump types also have more complex disposable elements than the peristaltic type pumps. In the drug delivery area, devices such as the hypodermic syringe that deliver a bolus of a drug or other active agent also present difficulties since the bolus must be gradually absorbed and delivered throughout the patient""s body, which is a process subject to many individual variances.
The Kamen family of pump technology (e.g., U.S. Pat. Nos. 4,600,401, 4,778,451, 4,808,161, and 5,193,990) in some respects attempt to solve some of the problems of the peristaltic pump, however, Kamen-type pumps have their own drawbacks. Kamen described a fluid movement technology based on the use of pneumatically driven diaphragm pumps and valves controlled by computer calculations of stroke volume displacement as a function of pressure and temperature. These calculations are time consuming and necessarily precise because the stroke volumes are small and the cumulative error must be kept minimal. Each stroke is interrupted by a long static period during which these measurements are made. In order to maintain the required average flow rate, the actual flow rate must be high, resulting in a step type of flow (a jump up when restarting the flow) which is detrimental, for example, to sensitive fluids in general, to many biological fluids, and to most types of cell separation processes, particularly the xe2x80x9cskimmingxe2x80x9d type cell separation processes commonly used in conjunction with centrifuges. (In a skimming operation, discontinuous flow and the jump of restarting flow, for example, in a photopheresis process, disturbs cell separation causing a flood of red blood cells in a plasma stream.) To compensate for the inefficiencies caused by discontinuous flow in a system using a Kamen-type pump, and its impact on, for example, a separation type process, additional fluid flow must be processed and procedure times increased.
Additionally, the Kamen family of pump technology requires a rigid disposable pumping or delivering/valving module which contains valve chambers that interrupt the laminar nature of flow in tubing, causing undesired mixing of separated components as the front flows through. This module (or cassette) is also typically costly and complicated to manufacture.
The present invention differs from the prior art, in that it allows, for example, for pressurized flow of a fluid without a pause in pumping or delivering. The present invention, in contrast to the Kamen pump family described above, allows, for example, for one continuous flow (i.e., xe2x80x9cpushxe2x80x9d) of fluid. The costly and complicated Kamen disposable pump/valve is eliminated. The present invention can be operated at much higher constant flow rates and average flow rates without the risk of high restart flow introduced in the Kamen system, as well as others, to catch up the average flow rate due to the pause and its related reduction in flow rate. The discontinuity and inefficiencies of the Kamen-type system and others are, therefore, addressed by the present invention.
Additionally, the present invention, in contrast to the centrifugal type pump, is or can be configured to be reversible. The present invention can also operate at a constant or modulated pressure to avoid the potential inherent in the peristaltic and other types of pump systems to develop excessive pressures, for instance, during an occlusion of the flow. The volume and other parameters of the fluid flow are accurately measurable in the present invention, in contrast to the diaphragm and centrifugal-type pump systems. The present invention may include, for example, a pressure limiting pump or direct weight measurement rather than a flow rate controlled pump, for added safety if a line associated with the pump becomes blocked or occluded. The present invention can also incorporate a minimal amount of noncomplex disposable elements and yet maintain, if desirable, the sterility of the pumping or delivering operation. Such sterility and minimized complexity may be particularly desirable when manipulating biological fluids such as pharmaceuticals and other active agents.
In comparison to pumps presently utilized in known processes or treatments, for example, the photopheresis and peritoneal dialysis processes described infra, the present invention can, for example: reduce total treatment or process time; reduce irradiation time (for photopheresis); allow increased flow rate; increase the total number of target cells collected or separated per total target cells processed (i.e., yield); increase the total number of target cells collected per treatment or process time; increase the total target cells collected per total volume of processed biologic fluid; reduce cell, fluid or fluid element damage in the process (e.g., reduced hemolysis); reduce contamination of target items collected (e.g., increase the percentage of target cells collected per total cells collected); operate with a reduced pressure differential; and, reduce flow rate differential.
The objects of the invention include providing a method and apparatus for providing a uniform and controlled flow of fluid. The invention relates to an apparatus and method for pumping or delivering fluids utilizing a flexible vessel subject to controlled pressures within an outer pressure chamber.
Certain of the objects of one or more embodiments of the present invention can, for example, in photopheresis and peritoneal dialysis procedures: reduce total treatment or process time; reduce irradiation time (for photopheresis); allow increased flow rate; increase the total number of target cells collected or separated per total target cells processed (i.e., yield); increase the total number of target cells collected per treatment or process time; increase the total target cells collected per total volume of processed biologic fluid; reduce cell, fluid or fluid element damage in the process (e.g., reduced hemolysis); reduce contamination of target items collected (e.g., increase the percentage of target cells collected per total cells collected); operate with a reduced pressure differential (i.e., reduce the variability of pressure in the system); and, reduce flow rate differential (i.e., reduce the variability of the flow rate in the system).
An additional object of one or more embodiments of the present invention is to reduce the amount of time that a patient""s blood is outside the patient""s body.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises a sealed flexible chamber adapted to contain a fluid or other pressure sensitive medium. This sealed flexible chamber can, for example, take the form of a plastic or other flexible bag, such as those typically used for storing and transferring sterile fluids, such as sterile biological fluids. This sealed flexible chamber is then disposed within an outer chamber. The outer chamber can take many forms, including a more rigid bottle or other housing and may be made of a myriad of materials including glass, plastic and the like.
The flexible chamber is part of a fluid path that extends beyond the exterior of the outer chamber by, for example, a catheter or other tube-like or other cannulated structure. The outer chamber is situated and constructed such that it can contain a pressure sensitive medium such as a gas or other fluid, such as air, for example, which can exert pressure on the flexible chamber.
This apparatus and method may include a means for increasing or decreasing pressure in a uniform and controlled manner within the space around the flexible chamber. Such means for increasing or decreasing pressure includes, for example, exposing the flexible chamber to reservoirs of gas or other pressurized fluids regulated at specific pressures or vacuum levels, or can take the form, for example, of any one of a myriad of standard pressurization pumps.
The disclosed method for pumping or delivering fluids includes changing the pressure within the space around the sealed flexible chamber such that fluid is displaced into or out of the sealed chamber in a uniform and controlled manner without or within the sealed flexible chamber.
The present invention and its preferred embodiments are particularly useful in the controlled flow of pressure sensitive fluids, such as, for example, certain biological fluids, and more specifically, in the controlled flow of blood or its cellular components.
The present invention also may include, in one or more embodiments, monitoring the increasing or decreasing pressure within the space around the sealed flexible chamber. The present invention may also include monitoring the volume, mass, weight or other properties of fluid displaced from or transferred into a flexible chamber. The present invention also may include, in one or more embodiments, the pressure sensitive medium of air or a gas about the flexible chamber disposed in the outer chamber.
In one embodiment of the present invention, the flexible chamber is filled with a fluid and that fluid is pushed, by applying pressure, into the environment outside of the outer chamber which may be, for example, a patient, or another chemical or manufacturing processor, by continuous means. The fluid flow is accomplished by the application of pressure into the outer chamber on the flexible chamber. The source of the pressure can be any standard pressure reservoir that is different (either greater or less than) the pressure surrounding the flexible chamber. If the pressure applied is less than that surrounding the flexible chamber (i.e., a vacuum), then the flexible chamber will displace the fluid out of the environment found outside of the outer chamber and into the flexible chamber. Conversely, if the pressure applied is more than that surrounding the flexible chamber, then the flexible chamber will displace the fluid out of the flexible chamber and into the environment found outside of the outer chamber. The present invention preferably accomplishes fluid flow without any discontinuity or disruption of flow until the source of fluid is depleted, the flexible chamber is completely filled or emptied, or until the differential in pressure around the flexible chamber is eliminated.
An additional advantage in one or more embodiments of the present invention, over the prior art, is that the flexible chamber obtaining or providing the fluid need not be maintained in a sterile environment for the process and fluid itself to be kept sterile. So long as the inside surface of the flexible chamber and the fluid itself are sealed off of the outside environment, the system will be sterile regardless of the environment outside of the flexible chamber.
The method of one of the preferred embodiments of the present invention disclosed herein, in the application of a separation system used in photophoresis or peritoneal dialysis systems as described supra, can perform the entire separation cycle with steady flow at regulated pressure through tubing uninterrupted by the sudden discontinuities of valve chambers. Mass flow preferably may be monitored by continuous direct weight measurement. The disposable pumping or delivering/valving module of the Kamen system is, thereby, eliminated.
Indeed, the method and apparatus of an embodiment of the present invention, in comparison to the known Kamen-type pump technology used in the UVAR(copyright) XTS(trademark) photopheresis system manufactured by Therakos, Inc., Exton, Pa., provide for one or more of: a reduction in total treatment or process time for the donor blood in the XTS(trademark) system; a reduction in irradiation time of collected buffy coat in the system; an increased flow rate of whole blood into the system, as well as collected buffy coat out of the centrifuge of the XTS(trademark) system; an increased total number of target cells (e.g., white blood cells) collected or separated per total white blood cells contained in the donor blood (i.e., yield); an increased total number of white blood cells collected per treatment or per unit process time; an increased number of total white blood cells collected per total volume of processed donor blood; a reduction of the contamination of collected white blood cells collected (e.g., an increase the percentage of white blood cells collected per total cells collected and/or decreasing the percent hematocirt in the collected buffy coat); and a reduced pressure differential and a reduced flow rate differential within the extracorporeal circuit.
In addition, the method and apparatus of an embodiment of the present invention, in comparison with the known peristaltic pump technology used in the UVAR(copyright) photophoresis system manufactured by Therakos, Inc., Exton, Pa., provide for a reduction in cell (red blood cell or white blood cell) damage (e.g., reduced hemolysis).
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one (several) embodiment(s) of the invention and together with the description, serve to explain the principles of the invention.